Automatic transmissions in which a clutch operation at the time of starting the vehicle and gear shift operations during running are performed automatically have been known.
Japanese Patent Laid-open No. Sho 56-57525 discloses a configuration of an automatic transmission for shifting among D (drive: forward running), N (neutral) and R (reverse: reverse running) positions in the transmission by a shift lever operated by the rider (driver), wherein the gear shift from N to D or R is not effected even if the shift lever is operated in the condition where the engine speed or the throttle position (throttle opening) is not less than a predetermined value. According to this configuration, for example in the case where the engine speed is high when the engine is started for starting the vehicle, the switching from N to D or R is inhibited, whereby exertion of a large driving force on the transmission is prevented from occurring.